1. Field of the Invention
The present invention relates generally to a portable radio terminal unit. More particularly, the invention relates to a compact portable radio terminal unit, such as a cellular telephone unit housing an antenna within a unit casing.
2. Description of the Related Art
Associating with evolution of mobile communication in the recent years, technical advancement and down-sizing of portable radio terminal are quickly progressed. In general, upon calling using the cellular telephone unit as the portable radio terminal, unless using earphone microphone or the like, user inherently use the unit holding in hand and placing the unit in the vicinity of a head. On the other hand, in case of key operation upon transmitting electronic mail message or the like or in case of watching a screen, the user uses the unit with holding in hand.
When the antenna is built-in a main body portion of the terminal unit for down-sizing of the unit of the portable radio terminal and for improving portability, it becomes necessary to make the antenna as small as possible. In such case, it is likely that the user may contact with a portion near the antenna by hand or user's head or users ear may be in close proximity of the antenna to significantly deteriorate antenna characteristics.
Namely, when the antenna is built in the unit body with down-sizing, it becomes necessary to mount the antenna at a position where the antenna does not contact with the head, hand, ear and the like. Selection of the mounting position is quite important for antenna characteristics. For instance, when the antenna is arranged on an upper portion of a casing (receiver side) of the terminal unit, the user's head is inherently positioned close to the antenna during voice communication to deteriorate the antenna characteristics. On the other hand, even if the antenna is arranged on a lower portion of the casing (microphone side) of terminal unit, when the antenna is mounted on the rear casing side opposite to the front casing where the operation panel is provided, the portion near the antenna can be covered by the hand of the user to be a cause of deterioration of the antenna characteristics.